1. Field of the Invention
This present invention is generally directed to auditory prosthesis, and more particularly, to an external speech processor unit for an auditory prosthesis.
2. Related Art
Hearing loss, which may be due to many different causes, is generally of two types, conductive and sensorineural. In some cases, a person suffers from hearing loss of both types. Conductive hearing loss occurs when the normal mechanical pathways for sound to reach the cochlea, and thus the sensory hair cells therein, are impeded, for example, by damage to the ossicles. Individuals who suffer from conductive hearing loss typically have some form of residual hearing because the hair cells in the cochlea are undamaged. As a result, individuals suffering from conductive hearing loss typically receive an acoustic hearing aid. Acoustic hearing aids stimulate an individual's cochlea by providing an amplified sound to the cochlea that causes mechanical motion of the cochlear fluid.
In many people who are profoundly deaf, however, the reason for their deafness is sensorineural hearing loss. Sensorineural hearing loss occurs when there is damage to the inner ear, or to the nerve pathways from the inner ear to the brain. As such, those suffering from some forms of sensorineural hearing loss are thus unable to derive suitable benefit from conventional acoustic hearing aids.
It is for this purpose that cochlear implant systems have been developed. Cochlear implants systems, sometimes referred to as cochlear implants herein, bypass the hair cells in the cochlea and directly deliver electrical stimulation signals to the auditory nerve fibres, thereby allowing the brain to perceive a hearing sensation resembling the natural hearing sensation normally delivered to the auditory nerve.
Cochlear implant systems generally consist of two components, an external component, and an internal or implanted component. The internal component receives signals from the external component that are used to provide a sound sensation to a user or recipient of the cochlear implant system, generally and collectively referred to as a recipient herein.
The external component includes a microphone for detecting sounds, such as speech and environmental sounds, a speech processor unit that converts speech into a coded signal, a power source such as a battery, and an external transmitter antenna coil. The speech processor unit outputs a coded signal representing a sound received by the microphone which is transmitted transcutaneously to a stimulator/receiver within the internal component. The stimulator/receiver unit is situated within a recess of the temporal bone of the recipient. This transcutaneous transmission occurs via the external transmitter antenna coil which is positioned to communicate with an implanted receiver antenna coil of the internal component. This transcutaneous transmission link is used to transmit coded signals output by the speech process unit and to provide power to the internal components. The transcutaneous link is, normally, in the form of a radio frequency (RF) link, but other such links have been proposed and implemented with varying degrees of success.
The implanted stimulator/receiver unit includes, in addition to the receiver antenna coil that receives coded signals and power from the external processor component, a stimulator that processes the coded signals. The stimulator outputs electrical stimulation signals to an intracochlea electrode assembly which applies the stimulation signals directly to the auditory nerve, thereby producing a hearing sensation corresponding to the originally detected sound.
The external component is configured to be worn by the recipient. For example, in certain circumstances, the external component may be carried on the body of the user, such as in a pocket of the user's clothing, a belt pouch or in a harness, while the microphone is mounted on a clip mounted behind the ear or on the lapel of the user. More recently, the physical dimensions of the speech processor unit have been able to be reduced allowing for the speech processor unit to be housed in a relatively small unit capable of being worn discreetly behind the ear of the user, sometimes referred to as a Behind-The-Ear (BTE) unit or BTE. In this arrangement, the external transmitter antenna coil is still positioned on the side of the user's head to allow for the transmission of the coded sound signal and power from the sound processor to the implanted stimulator unit.
BTEs have provided a degree of freedom and subtlety for the recipient which has not traditionally been possible with body worn devices. There is no longer a need for extensive cables connecting the body worn processor to the transmitter antenna coil, nor is there a need for a separate microphone unit or battery pack, as the BTE unit contains all the components in one housing. One common feature of all conventional BTE units is the provision of a dedicated mechanical switch for turning the unit on or off. Such a switch is typically small in size and difficult to manipulate, especially in the case of elderly recipients or those who are not very dexterous. Continuous use of the switch causes mechanical fatigue resulting in the switch failing to operate and requiring repair or replacement.